? android中l(wèi)auncherMode有4中屬性：standard(默認)， singleTop，singleTask和 singleInstance；網(wǎng)上有好多例子講解這四種關(guān)系的：下面我列舉幾個鏈接：

?????? 大明原創(chuàng)---->轉(zhuǎn)載請標明出處：http://blog.csdn.net/wdaming1986/article/details/7304191

??????? http://www.cnblogs.com/xiaoQLu/archive/2011/09/29/2195742.html

?????? ?http://marshal.easymorse.com/archives/2950

??????? http://blog.csdn.net/infsafe/article/details/5666964

??????? http://www.j2megame.com/html/xwzx/ty/2027.html

??????? 等等。我不一一列舉；

?????? 下面是我對singleTask的一點拙見，希望分享一下給大家：

??????? 最近研究android瀏覽器browser，這個BrowserActivity的launcherMode="singleTask"，因為browser不斷地啟動自己，所以要求這個棧中保持只能有一個自己的實例，就像別人總結(jié)的這樣“注意：singleTask模式的Activity不管是位于棧頂還是棧底，再次運行這個Activity時，都會destory掉它上面的Activity來保證整個棧中只有一個自己，切記切記”這點是毋庸置疑的。

?????? 問題：browser的launcherMode=“singleTask”，browser上網(wǎng)的時候，遇到播放視頻的鏈接，就會通過隱式intent方式跳轉(zhuǎn)找Gallery3D中的MovieView這個類來播放視頻，這時候如果你點擊home鍵，再點擊browser，你會發(fā)現(xiàn)MovieView這個類已經(jīng)銷毀不存在了，而不會像保存這個MovieView的類對象，給客戶帶來的用戶體驗特別的不好。用戶還得從新下載剛才的視頻。不支持斷點播放。為了驗證這一問題，我專門寫了個小例子來說明activity之間的生命周期：

?????? （1）先建一個App1的工程。包名為：com.cn.daming.app1，包里面有一個類：App1Activity。里面的代碼如下：

[java] view plaincopyprint? package?com.cn.daming.app1;????import?android.app.Activity;??import?android.content.Intent;??import?android.os.Bundle;??import?android.util.Log;??import?android.view.View;??import?android.view.View.OnClickListener;??import?android.widget.Button;????public?class?App1Activity?extends?Activity?{????????private?Button?mButton?=?null;????????????@Override??????public?void?onCreate(Bundle?savedInstanceState)?{??????????super.onCreate(savedInstanceState);??????????setContentView(R.layout.main);??????????Log.v("daming",?"App1Activity--11-->onCreate()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????????mButton?=?(Button)findViewById(R.id.button1);??????????mButton.setOnClickListener(new?OnClickListener(){????????????????public?void?onClick(View?arg0)?{??????????????????Intent?intent?=?new?Intent();??????????????????intent.setClassName("com.cn.daing.app2",?"com.cn.daing.app2.App2Activity");??????????????????startActivity(intent);??????????????}??????????});??????}????????@Override??????protected?void?onDestroy()?{??????????super.onDestroy();??????????Log.v("daming",?"App1Activity--11-->onDestroy()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onPause()?{??????????super.onPause();??????????Log.v("daming",?"App1Activity--11-->onPause()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onRestart()?{??????????super.onRestart();??????????Log.v("daming",?"App1Activity--11-->onRestart()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onResume()?{??????????super.onResume();??????????Log.v("daming",?"App1Activity--11-->onResume()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onStart()?{??????????super.onStart();??????????Log.v("daming",?"App1Activity--11-->onStart()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onStop()?{??????????super.onStop();??????????Log.v("daming",?"App1Activity--11-->onStop()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onNewIntent(Intent?intent)?{??????????super.onNewIntent(intent);??????????Log.v("daming",?"App1Activity--11-->onNewIntent()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onSaveInstanceState(Bundle?outState)?{??????????super.onSaveInstanceState(outState);??????????Log.v("daming",?"App1Activity--11-->onSaveInstanceState()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}??}??

?????? manifest的屬性為：android:launchMode="singleTask"???? android:alwaysRetainTaskState="true"

?

????? （2）在建一個App2的工程，包名：com.cn.daing.app2? ；類名為：App2Activity；代碼為：

[java] view plaincopyprint? package?com.cn.daing.app2;????import?android.app.Activity;??import?android.content.Intent;??import?android.os.Bundle;??import?android.util.Log;??import?android.view.View;??import?android.view.View.OnClickListener;??import?android.widget.Button;????public?class?App2Activity?extends?Activity?{????????????private?Button?mButton?=?null;????????????@Override??????public?void?onCreate(Bundle?savedInstanceState)?{??????????super.onCreate(savedInstanceState);??????????setContentView(R.layout.main);??????????Log.v("daming",?"App2Activity--22-->onCreate()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????????mButton?=?(Button)findViewById(R.id.button1);??????????mButton.setOnClickListener(new?OnClickListener(){????????????????public?void?onClick(View?arg0)?{??????????????????Intent?intent?=?new?Intent();??????????????????intent.setClassName("com.cn.daming.app1",?"com.cn.daming.app1.App1Activity");??????????????????startActivity(intent);??????????????}??????????});??????}????????@Override??????protected?void?onDestroy()?{??????????super.onDestroy();??????????Log.v("daming",?"App2Activity--22-->onDestroy()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onNewIntent(Intent?intent)?{??????????super.onNewIntent(intent);??????????Log.v("daming",?"App2Activity--22-->onNewIntent()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onPause()?{??????????super.onPause();??????????Log.v("daming",?"App2Activity--22-->onPause()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onRestart()?{??????????super.onRestart();??????????Log.v("daming",?"App2Activity--22-->onRestart()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onResume()?{??????????super.onResume();??????????Log.v("daming",?"App2Activity--22-->onResume()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onSaveInstanceState(Bundle?outState)?{??????????super.onSaveInstanceState(outState);??????????Log.v("daming",?"App2Activity--22-->onSaveInstanceState()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onStart()?{??????????super.onStart();??????????Log.v("daming",?"App2Activity--22-->onStart()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????@Override??????protected?void?onStop()?{??????????super.onStop();??????????Log.v("daming",?"App2Activity--22-->onStop()...."+"?/n?getTaskId()?==?"+??????????????????getTaskId()+"???isTaskRoot()?==?"+isTaskRoot());??????}????????}??

???? manifest的屬性為默認值；

???? （3）然后啟動App1---->點擊調(diào)用第二個App2button按鈕的log：?

????????????????????? ?

? ??? 從log中可以看出：從App1到App2是在一個task棧中，值都是33，并且App1Activity是位于棧底。根節(jié)點的。點擊按鈕的時候，調(diào)用App1Activity的onSaveInstanceState()----->onPause()----->App2Activity的onCreate()----->onStart()---->onResume()---->App1Activity的onStop()方法。

?

???? （4）點擊調(diào)用第一個App1---->button按鈕；

???????????????

???

?????? ?看一下log：

?還在一個棧中，數(shù)字變了因為我退出后從新操作的，把以前的log清空了，這時候發(fā)現(xiàn)了一個奇怪的現(xiàn)象，啟動第一個App1的時候，App2從onStop()---->onDestroy()了，徹底銷毀了；這個對象就不存在了。這也就驗證了browser點擊視頻播放，點擊home鍵，再點擊browser，視頻播放停止的現(xiàn)象的，android的singleTask就是這個設(shè)計的。挺獨特的。

??????（5） 要想解決這一個問題，也是有辦法的，我經(jīng)過兩天的鉆研，終于找到了方法，現(xiàn)分享給大家：就是在App1中啟動一個activity，這個activity的launcherMode=“standard”，然后由它來啟動App1Activity，這樣就避免了這一現(xiàn)象;

????? 啟動一個默認的activity：LoginApp1Activity代碼：

[java] view plaincopyprint? package?com.cn.daming.app1;????import?android.app.Activity;??import?android.content.Intent;??import?android.os.Bundle;????public?class?LoginApp1Activity?extends?Activity{????????@Override??????protected?void?onCreate(Bundle?savedInstanceState)?{??????????super.onCreate(savedInstanceState);??????????Intent?intent?=?(Intent)getIntent().clone();??????????intent.setClass(LoginApp1Activity.this,?App1Activity.class);??????????startActivity(intent);??????????finish();??????}??}??

??????

?????? ??manifest.xml中的代碼：

[html] view plaincopyprint?